Got yet another one for the forums. Earlier today, I was working with Hydrocal for the first time in quite a while. I was trying to build a tunnel liner using the Woodland Scenics Tunnel Liner mold. In the process I ended up with a bunch of problems. First, when I tried to put the Hydrocal in the mold, it ran all over the place creating quite the mess. (Most of it was on an unfinished plywood floor, so that wasn’t a problem.) In that process, I was unable to get the back (top surface) of the mold completely level. After I managed to get it reasonably level, I let it sit for the 40 minute cure time. When I tried to clean the excess off, I found that even after letting the casting cure even more, that the material was not anywhere near what I would have expected for hardness. As a result, I ended up throwing the entire casting onto the trash pile.
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My questions are these: Did I do something wrong with the mixing that caused the Hydrocal not to work? Should I have waited longer before putting everything in the mold? Was I not patient enough before I tried to remove the casting? Is there anything else that I need to know about the liners?
As usual, any assistance the forums can provide will be most welcomed.
I would say it was too thin. I’ve used that process a lot starting off using Plaster of Paris to make tunnel walls and that worked good but Hydrocal works better. That being said if you mix either too thin it is super runny. I mix my batches thick almost like a molding mud that you can work with your hands. Hydrocal sets up quickly when mixed thick so you can’t dally.
Edit:
I use touchy-feely method for demolding my castings. Both Hydrocal and Plaster of Paris heats up as it cures when it starts cooling down it’s ready to remove.
If you have a lot of tunnel sections to make be very careful with the WS plastic mold as it will crack easily. Work the mold off starting at the long end.
I’ve really never followed the manufacturers directions, as a kid in the 40s my Mother made Plaster of Paris figurines and I was the pre teen “mixer”. We would spend hours filling molds with me mixing so it’s a natural thing for me.
I don’t use a ratio, I add water to the powder until it becomes thin enough to poor, like an old fashion thick milkshake. One important thing is do not become a tight wad and try to salvage leftover plaster or Hydrocal, once it’s mixed and it has started to setup disturbing the ratio by adding either water or powder screws it up!!! If you need more toss the old and do a restart.
As Mike said for added strength imbed some coarse fabric to the outside of the casting. I’ve been using a 2” wide medical wrap from the local pharmacy, the stuff they use making casts. You can use a spray bottle of water to wet the plaster and use the gauze strip as joiner tape. Mix a soupy batch in a bowl and dip the material in it and apply to the wetted plaster casting like making a broken bone cast.
Was the casting crumbly after it hardened? How old is your Hydrocal, and how have you had it stored?
I got down near the bottom of a big container of Hydrocal one time and had that problem. I think the Hydrocal had absorbed water in its years in the jar, and once that happened it just wasn’t going to work anymore. New Hydrocal, no problem.
I sometimes make curved castings by bending a flat casting around a form after the Hydrocal has set up for about 8-10 minutes. I use clear plastic wrap over the back face of the casting. In your case, you might try pouring the Hydrocal and gently rocking the mold back and forth while it sets up.
It’s a bit off-topic, but this is how I did the interior walls in my subway system:
I bought a large sheet of styrene and cut it into strips. Then, I mixed a thin slurry of Hydrocal and applied it with a paint roller. This is basically how textured ceilings are done. I let it set and sprayed it first with gray primer and then with just a mist of black. At that point, the styrene strips held the Hydrocal but they were still flexible enough to bend them and attach them to the foam walls of the tunnels.
Sounds like maybe your Hyrdocal is old, so may not be a formula issue. However, if I was going to modify the formula for this specific app, I’d go with either 1.5 plaster to .5 water OR 1.25 plaster to .4 water. Basically bump it 10% to 20% toward a drier mixture.
One way to do this is to simply measure the standard amounts, then only pour part of the water in, adding it little by little until you get just enough to get it wet or a little more. It won’t be as strong as it could be, but you don’t need a lot of strength here, just get it to stay in the mold until it dries.
Bob,
Good idea! Gotta love how Sculptamold is so versatile. The advantage it has over the WS molds is that it’s very customizable, especially with curved tunnels…
But you could actually use the WS mold and fill it with Sculptamold, too. It’s going to be much easier to fill and cast with the mold and it holds detail darn near as well as Hydrocal. Plus it won’t break anywhere near so easily and will be lighter than a version cast with plaster of any kind.
That is an interesting idea. I was eventually going to have to get some Sculptamold for my hills anyway, so that might be a good way to kill two birds with one stone as it were. (As I have a lot of Hydrocal portals and retaining walls on my hills anyway, keeping stuff light is a very good idea. And those hills aren’t exactly small either. One of them is roughly 5 feet tall by 2-2.5 feet wide and the other is 2 x 2-2.5 feet. Built from beadboard stryofoam.)
Am I correct in presuming that one would use a putty knife or something similar to put the Sculptamold into the liner mold? As I remember Sculptamold is fairly thick when it is mixed. (It has been awhile since I used that item as well.)
One of the great things about Sculptamold is that you can vary the moisture content accordling to need. It’s much less sensitive to that than plaster, where you can’t get too far off from the specfification or things start going wrong.
I’d take a suitable amount and add water and mix until it’s evenly wet and works easily so you can push it into the mold. A yogurt cup or similar size container woulld allow you to mix a batch right in it. A good stiff-bladed putty knife is ideal for mixing and applying it.
I actually have a couple of MIcro-Mark flexible rubber bowls that I used today to make a couple of batches of the Sculptamold. (Something that I had hiding in my old bedroom at the ranch where I grew up. My Mom found them when she was cleaning and, of course, had no idea what they were! But that’s another story entirely.)
With a little bit of practice, the Sculptamold was quite easy to work with. In the process, thought, I have run into a slight problem: I ended up with air bubble remnants in the castings. (The four that I have can be used in hidden areas as the tunnels aren’t daylighted all the way throught.) I presume that I didn’t vibrate the forms enough.
What would be the best idea for solving that problem in the future? The best idea that I can come up with would be one of the cheap 3-legged vibrators that a certain box store carries. If there are any other ideas, please let me know.
That sounds about right. You don’t want it soupy or even a slurry. But you want to work up the flavor or binder stuff so it’s nice and wet to fill those bubble spaces instead of air.
I mounted my mold to a piece of wood IIRC. Tapping it could help, I was just thinking that the secret is in the sauce on this more than technique. Don’t be afraid to add more water right at the beginning if not mixing wet enough for you. Same with throwing in some more Sculptamold if too wet. Unlike with plaster, this won’t hurt if you’re still mixing and haven’t stopped stirring yet, so to speak.
I tried the idea of my 2:3 mix on Saturday while waiting for family plans to come together. Unfortunately, for some reason that mix ended up way too wet. The castings ended up too thin and even after 24 hours (approx.) the castings hadn’t cured. They broke apart when I tried to unmold them. I also discovered that even with that mix the castings ended up having air buble remnants. I ended up using the pieces which were still flexible (Play-Dough consistency) and plugged some scenery holes with it.
I then tried a 1:1.25 mix. While that mix still had a few bubble remnants, it cured fairly quickly and I was able to unmold them easily. I think I will run with that mix as it molds nicely and it also is nice to work with when I’m covering hills.
I’ve got two questions as I’m finishing up scenery on my MR. First, how many of you finish the insides of your tunnels. Not sure if I should finish up the plastering inside or just paint it black and be done with it. Or better said, how many of you show off your tunnel’s inside as part of your layout.
Question 2: I’m at the point of finishing up my operating drive-in theatre. Need suggestions on gravel to use for the parking lot. Wasn’t sure if I should use ballast or some other type of “gravel” for this. Need kind of a bleached out color. I know ballast does come in various colors just wasn’t sure if this would be too course for the lot. Many thanks!
I put full scenery in my subway tunnels, but the whole idea was to create the right environment for the video camera in the first car of the subway train.
http://www.youtube.com/watch.php?v=dOV9NSqrQlc
I personally enjoy the video camera effect, and as I put more above-ground scenery in, I bring the subway up every now and then and watch the show on TV. It’s a big hit with the spectators, too, particularly the kids.
For my subway walls, I used strips of styrene. I took a hint from the textured ceiling, and applied Hydrocal with a paint roller, let it dry and painted it with light gray primer. My tunnels are lighted inside. The video was taken a long time ago, and since then I’ve added a couple of bright LEDs to the front of the train to improve the lighting.
I recall visiting a club that had two very visible tunnel interiors, protected with plexiglas. The double track main paralleled the aisle on two different levels. One had been finished with a rough, ‘blasted through the granite’ appearance. The other was finished with a concrete lining, including safety bays. Both were a couple of yards long, the effect was impressive and only the club members knew that the tracks were on opposite ends of a lengthy main line.
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My ‘maybe in the future’ plan book includes a similar underground diorama of a brand-new bore being cut by an operating TBM. It’ll probably get built shortly after I dock the Emma Maersk at my intermodal port.
Chuck (modeling Central Japan - 200 KM from the nearest salt water - in September, )
Can we assume that this is H0?
Humour can be fun… BUT you do not want people leaning over to look into the tunnel! They will catch things with their clothes and limbs. [:O]
You may want to think more about how you are going to do maintenance in a tunnel than how you will scenic it…
You do not want to make a tunnel a dust trap, somewhere nice for bugs/vermin to live or somewhere you have to use an endoscope to do any work in… including just getting out a last car that got uncoupled…
Where your tunnel is somehow close to a viewing face of the layout (like if you have a hidden curve in the tunnel) it cn be fun to be able to look in and see the train in the tunnel through like a horizontal mine shaft. (Cut in from the front of the board… as distinct from looking in the tunnel mouth) If you do that it gets to be worth detailing the tunnel wall that you will be able to see. You will also quite likely want to arrange some illumination… LOW temperature!
About the most important thing is to be able to keep up the maintenance on this part of the layout.
Ballast/gravel road surface.
If you can go get some road surface material and a piece of ballast. Hold both in your hand and compare all three… then look at the size of the hand on one of the figures on your layout.
Ballast does get degraded and get dirt in it… BUT it starts out passing through a 2" ring in the screening process and isn’t much smaller. You would not want to walk around a drive in theatre if it were lossely paved with (old) ballast. (Okay, it
This is HO scale, forgot to mention that. I purchased some fine grade ballast in light gray yesterday and it seems to look pretty good. I do sift my groundcover a second time with a fine strainer and you’d be surprised on how much doesn’t make it through the screen. I went ahead and built up the parking lot humps and just need to cover the lot but not before adding the speaker poles that hopefully I can get to light up.
The two side by side tunnels I have are curved and about two feet long. The top is made to pop off for maintenance and uprighting derailed cars. I thought about putting in a hobo camp or something halarious in the tunnel. The hard part is being able to blend in the pop offs so you can’t see any creases or gaps between the top and tunnel itself. So I went ahead and placed the top on an oversized piece of very thin styrene and blended in the scenery. Essentially the tops just sit without any adhesion to the tunnel itself. Thanks for all the great help! [8D]
Steve,
An interesting read, especially the tunnel comments as I am builing mine now.
Whew, I built the mountains, really liked them, used some paper rock homemade portals and stopped cold. Why? I realized I need to ‘line my tunnels’. OK, so I built some ‘paper and cardboard’ liners. I fitted them in from the back. Yuk, the paper portals looked awful. ANd the lines were only a bit better.
So I purchased some plaster portals and fitted them to my paper liners. Even more yuk! So I built some styrene liners and started installing them and the plaster portals. Ready to glue it down and stopped cold again. I needed to paint the styrene tunnels which turned out to be no trivial task as the acrylic paint bubbles on dirty plastic. (First time I tried to paint any styrene with acrylic paints you know). OK, painted lets glue. Oh no! The track needs to be balasted but the roadbed needs to be painted first.
At that point, I was glad my mountains were light and removable, so off they came, and I started ground up.
widen roadbed so tunnel liners have no gaps. I use 3/4 masonite strips glued to the sub road bed edges like they do in spline roadbeds to fix narrow places on the roadbed.
Paint roadbed very dark grey
Align track one more time and replace missing ties.
Ballast track all the way past the liner and outside the portals
Check liner paint job
Trimed liners to fit with retaining walls
Paint and weather the portals and retaining walls. What a kick that was!
Glue liner to portals
Glue portals to roadbed
Installed retaining walls
Reinstalled mountains
Plaster cloth repairs to mountain shells
Now ready to so some scenicing.
Never did I realize it was so involved in making mountains and portals and such. But boy do I like the results.
I’ll post some pictures later, gotta run!
I am not unduly fond of tunnels but I have had a few of them on my (N-Scale) layouts over the years. None have ever been long enough to swallow up more than a dozen or so cars of a train.
If the tunnel in question is straight I usually put a flat black tinted lining stretching 5" to 6" in from the portal. I always leave the middle of the tunnel open, at least on one side to facilitate operation of my 0-5-0 switcher. I don’t use as long a tinted lining with a curved tunnel as with a straight one.
I heartily recommend leaving 0-5-0 switcher access into your tunnel. Bill McClanahan of Texas and Rio Grande Western fame once did a cartoon to accompany one of his magazine articles which showed a character with a fishing pole jabbed into the mouth of a tunnel while he tried to retrieve a derailed car with a fishhook. Believe me, you have never known the height of frustration until . . . . . . . . . .
If you don’t use ballast for gravel what are you going to use???
I haven’t been to a “passion pit” since and I’m not sure I ever went to one with a gravel parking area; I will presume, however t
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